PredictableSpecificityfor Differential Measurementof Choriogonadotropin and ItsSubunits
نویسنده
چکیده
Knowing the epitope specificities of our monoclonal antibodies (MCA) to human choriogonadotropin (hCG), we could design three classes of two-site immunoradiometric assays (IRMA): a combinationof two MCA recognizingtwo separate a-epitopes (a-MCA) provides a system (i.e., an a-IRMA) that measures holo-hCG plus free a-subunitsplus follitropin, lutropin, and thyrotropin, whereas a /3-IRMA, consistingoftwo /3-MCA, quantifies holo-hCG plus free /3-subunits. The amount of either of the two subunitscan be calculated by subtractingthe amountof holo-hCGdeterminedin parallelin a holo-hCG-IRMA. In the latter,one of the aor f3-MCA may be eithercross-combinedor,preferably, pairedwithan MCA specific for a conformationalepitope.These analyticalspecificities, predicted from our previously established epitope map of hCG, could be experimentally verified. With these IRMAS we could demonstrate that in certain choriocarcinoma celllinesthe earliest and quantitatively predominanttumor marker is the free a-subunit. Similar results showing an unbalancedsecretionof hCG and itssubunitswere obtained for patients with related tumors. These findings challenge the present diagnostic practice of relying solely on “p-hCG” radioimmunoassaysand at the same time offer a novel analyticalstrategy.
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